= S. D. Eilen
{c}
\b[S. D. Eilen] is the first author of a 1983 study comparing <palpation> of the <apical impulse> with two-dimensional <echocardiography> as evidence of left ventricular enlargement. The investigators examined 41 patients and compared surface observations with <end-diastolic volume> measurements.<Accuracy of precordial palpation for detecting increased left ventricular volume by S. D. Eilen and others>[Byline and Abstract]{ref}
The study found that impulse location relative to selected chest landmarks alone was not a reliable indicator of increased ventricular volume.<Accuracy of precordial palpation for detecting increased left ventricular volume by S. D. Eilen and others>[Abstract, conclusion about location]{ref} Its scientific contribution is a test of a physical sign against an independent imaging measure, rather than an assumption that the visible or palpable position directly reveals chamber size.
An original classification example shows why different accuracy quantities must be separated. Imagine 100 subjects, 40 with the target enlargement by an independent reference. A test detects 24 of those 40 and also flags 6 of the remaining 60. Its <diagnostic sensitivity> is $24/40=60\%$, while the fraction of positive findings confirmed by the reference is $24/(24+6)=80\%$. These invented counts are not the 1983 study's data.
The first fraction conditions on the reference-defined group; the second conditions on the observed positive group. Changing which subjects enter a study can change their relationship. The example clarifies why a useful account of a physical sign identifies the observation, comparison measurement and study population. Eilen's published initial-only byline is retained without inferring a full identity or unrelated career history.
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